DIY pancake slip ring

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qauker
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DIY pancake slip ring

Post by qauker » Fri May 21, 2021 6:49 am

Guys making a flat " pancake" slip ring

Simply to transfer electrical power to a rotating platform .But it needs to be flat not cylindrical
Does anyone know where I can buy strips of sprung metal electrical contacts ? Such things are everywhere in battery connectors, RFI shielding, tiny dc motor commutator brushes, electro mech relay contacts. But I cant find anywhere to buy eg a sheet of the stuff I can cut into strips to suit .

Any ideas ? Attach a photo of one of the many unsuccessful efforts in making the rotor with old relay contacts , Just a bit too small


Grateful for any pointers
PS If interested : A guitar jack plug is a simple slip ring. A contact " brushes against a metal body . To make a slim pancake one You might think a "lazy susan" would provide the obvious rotating mechanical platform. Not so. Can provide further if interested Hopeful if I can find the contacts mine will be four channel and just 6mm depth .
ciao MsO
Attachments
cock up rotor.JPG


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haklesup
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Re: DIY pancake slip ring

Post by haklesup » Tue May 25, 2021 1:13 pm

Mill-max has some spring pins (pogo pin style) in plastic strips, the omniball is specifically designed for this application

https://www.mill-max.com/products/new/o ... ed-contact
https://www.mill-max.com/products/new/o ... ct-options

if you want stamped and formed springs, check out SIB at Samtec though I can't say how well these work as sliding slip ring contacts, you should contact their support for advice if going this way.
https://www.samtec.com/products/sib

qeuker
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Re: DIY pancake slip ring

Post by qeuker » Sun Jul 04, 2021 12:44 pm

guys pardon delay response May I please thank all who have responded
I will pursue all the links you have given to find that material
Yes there was a similar on Robot shop but that seems abandoned .

A little more on the project It HAS To be a Pancake (Flat profile) slip ring for this application Flatter the better
My mechanics look like I can get to just 6mm profile So no to " guitar jack plugs / or any tubular standard slip rings.
Have seen a manufacturer of " pancake rings" at approx £1000 a pop/ nitrogen gas filled etc min 12 mm Too thick Twice mine.

I only need to transmit power to a tiny 0.5A geared dc motor + 2 other switches. Have to go cooking my own recipe then LOL
If I do it I reckon I will float on the stock market !
Anyone in the Wimbledon London SW19 ( tennis) area that has a 3d printer and small workshop better than me sawing between my knees?

Someone said old video players had a good slip ring in them ? cant see that m'self All the best guys

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jwax
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Re: DIY pancake slip ring

Post by jwax » Wed Jul 07, 2021 6:32 pm

Wireless cellphone charger coils could get your DC power, although with added circuitry.
What are the other 2 contacts for?
WA2RBA

qeuker
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Re: DIY pancake slip ring Cell phone charger

Post by qeuker » Sat Jul 10, 2021 4:13 am

Hello Jwax

thanks you so much suggestion cell phone charging concept " Power transfer to jump the gap " I slept on that.. A "lazy Susan" levitated ? Sadly I cannot see how that could achieve rotation of a disc. At least not without re jigging -inventing the synch / stepper motor. ?

If you think of a lazy susan mechanism: Then to think how to rotate the upper disk ? The constraints of no external drive to the perimeter, and We only have 6mm depth below that disc for anything else ( direct motor) So any concept of belt drive ( record player style) is No. I cannot find any motor slim enough to fit under a 6mm gap even though rotation speed is very low and load is only light . ( not that is affordable anyway)
So there is only one solution ?

The dc motor has to rotate WITH the table It drives against the lower fixed part. So slip ring required ? (the other two tracks are there as I might as well cut two as cut four for the stator)
Again big thanks to all who responded . Just stuck to find contact material for the rotor. Wrote to some manufacturers as links were given. Alas as so often if you are not customer wanting 10,000 of their standard products. Very doubtful to get any reply. Never thought it would be so elusive to source
( electrical sprung contact material)
so Anyone got any old ( larger) relay contacts to sell me or similar ? ciao Thanks again to all I might just go to by a ready made ring and try that as on link given . very expensive and still would have to adapt Takes the fun out of it. I've come so far with recycled materials to make this M O

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Janitor Tzap
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Re: DIY pancake slip ring

Post by Janitor Tzap » Sat Jul 10, 2021 7:10 am

Sorry to be responding so late, but I've been having a lot of family issues going on. :sad:

I don't know how big this ring has to be.
But how about using old HO-Gauge Slot-Car Track?
Image
You could then use cars pickup brushes.
Image
Or use those Ball Contacts that haklesup mentioned.


Signed: Janitor Tzap

qeuker
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Re: DIY pancake slip ring

Post by qeuker » Sat Jul 10, 2021 9:46 am

Mr Janitor I just love the ingenuity of the suggestions still coming in Thank you so much and YEP there is a ready made stator 4 channel
and the car(s) would make the rotor and even have the little motor in them . I'm thinking if I can adapt The radius of the stator with HO gauge would be far too big BUT it is an idea that might make production of the stator easier than cutting rings from copper plate.
But brings me back to the question so frustrating me . Where can I buy ( eg model car ) spring electrical pick ups ?

Hereas another idea (after thinking again about jwaxcell phone idea) How about a slim escooter style hub motor Wonder if anyone makes a flat slim version of that Then at least the rotation issue with all sides of the ring free would be solved. Any slim hub motors suggestions ciao msO

qeuker
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Re: DIY pancake slip ring

Post by qeuker » Sat Jul 10, 2021 9:51 am

ps : I looked at the ball contacts .. woudl heve been godd BUT the smallest one they make comes in a 10mm or so tube sprung loaded
Have tried to use carbon brush but so difficult to mount ( spring load ) and wouldn't last long with just a 4mm or so depth .

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Janitor Tzap
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Re: DIY pancake slip ring

Post by Janitor Tzap » Sat Jul 10, 2021 3:48 pm

qeuker wrote:
Sat Jul 10, 2021 9:46 am
But brings me back to the question so frustrating me . Where can I buy ( eg model car ) spring electrical pick ups ?
Check E-bay, Craigslist, and several slot car hobby sites.
Check out local garage sales, or flea markets.
You can find complete sets with the track, cars, hand speed controllers, and power supply for a reasonable price.
Or just the individual pieces.


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qeuker
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Re: DIY pancake slip ring

Post by qeuker » Thu Jul 15, 2021 3:21 am

Guys I guess time to give up Still no cigar . Researched " sprung electrical contact"
Many learned phd articles nothing practical

Taken a chance on a roll of something coming from china Maybe this is it ... Maybe we should commission a "practical guide to sprung electrical contacts in robotics" Nothing out there at all for such a basic need

"It might be you " or me, see what turns up from China ...brexit delays// taxes Thanks again to all who gave their time and suggestions to this thread. all the best Ms O

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Lenp
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Re: DIY pancake slip ring

Post by Lenp » Mon Jul 26, 2021 4:18 pm

Don't know it this slip ring project is still of interest, but if it is here's another idea.
Make two non-conductive disks, diameter as required, with a center hole in each.
Make two (or more) rings from a flat copper sheet that will be concentric to one each other and fit on the disk. fasten as desired, epoxy or even small screws if possible. These are the slip rings.
Get two, or more round motor brushes, with springs, and a piece of brass tubing that the brush will comfortably slip into. Close off one of the tube so the spring is captured. Drill 2 holes in the other disk that align with the center of the copper rings and are a snug fit for the brass tubing. These are the brush holders. Use a center shaft and a thrust bearing in the center to keep it all aligned. Use more brushes strategically placed to give better support and alignment if needed.
Bit parts cane be found at https://www.mcmaster.com (No affiliation!)
If there is interest I can cobble together a drawing and post it.

Hope this helps.
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

qeuker
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Re: DIY pancake slip ring Unsolved yet Study ?

Post by qeuker » Tue Jul 27, 2021 3:22 am

thanks again all. Do we need a separate study forum for this ?? The quest is this : What material is used for sprung electrical contacts and where can you buy it ?
How little we seem to know of the material used for this most common and ancient method of transmitting electrical power It is all around us Battery holders/ electrical machines / mobile phones / electro mech relay contacts/ guitar jack plugs/ connectors you name it...
Just about any electrical project / robot etc will use sprung electrical contacts somewhere ....


Len Thanks stator rings on a plastic plate Yep ,what i've done (bit more) Rotor traditional carbon brush contacts .. NO GO they take too much vertical space Target overall depth is 6mm . Including plastic housings. Only a metal contact can do it (as far as I can see.) . After much research I've taken a chance and ordered some material from China . ( no one else offers) Let you know if this at last is some answer. I made 6 experimental stators with old relay contacts.. they lasted oneor two rev and fell out !! lol (Brown paper and vinegar not so good )
Flat( ish) pancake slip rings are manufactured Expensive , you see on those ads the rotor with metal contacts. ( I put a picture up ) But what is it made of ?? Where do all these engineers get the material from Nuts and Volts ??

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haklesup
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Re: DIY pancake slip ring

Post by haklesup » Tue Jul 27, 2021 2:02 pm

the material of choice for electrical contacts is BeCu with gold plating. The Berrillium copper alloy is harder than pure copper and can be machined or stamped into shape and it will retain that shape and can be heat treated for other properties like spring tension. The gold plating passivates the surface from corrosion and improves conduction or electricity because it is not as good as pure copper. This material is more brittle and breaks more easily than pure copper. The alloy may be tweaked for stamped pins vs machined pins.

These guys can make custom stamped pin electrical contacts but it will cost a little bit in terms of NRE and Min qty orders

https://fotofab.com/electrical-contacts/
https://www.vaga.com/materials/beryllium-copper

My experience is that if you can do it with a spring pin or off the shelf component, it will cost less overall. This solution is better for high volume or cost is no object prototypes.

For off the shelf you are back to mil-max and samtec, elpacko . "Leaf pin electrical contact" got better image search results than Stamped pin FWIW as did "sliding electrical contact"

If you still feel you know too little, I'm sure its overkill for your question, but here is a comprehensive book on the topic (I have a paperback copy here)

https://www.amazon.com/Electrical-Conta ... 7966809735

qeuker
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Re: DIY pancake slip ring

Post by qeuker » Wed Jul 28, 2021 10:58 am

hello haklesup Thanks.
OK we are half way there to our DIY /Nuts and Volts How to ? quest on the subject with your contribution . Hope my order for CU beryl roll arrives sometime soon from China ... Oops You comment It can be heat treated to make it springy... Oh hope it was already springy LOL Still we try
Yes It too found many academic articles on the subject. sadly rather beyond with no practical example.

Thankyou industrial links yes I will try again to ask advice ( how to make it springy ) and can they supply with a small sheet or so for my prototype application ( see photo "cockup rotor) but NEVER has any such company producing such components bothered to reply to the single low use inventor I dont expect
I can still be practical
If anyones interested we have Cu/beryl " sheet" arriving If its not springy I'll try my blow torch on it ( thanks Haklesup) LOL New topic "Make our own sprung electrical contacts if your interested . Could be bet its actually not very difficult ? ...

thanks again to all who have contributed If it can be achieved at reasonable cost then I think a flat slip ring has so many applications

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